[Ke Yin Network () News] Flexo has gradually become the mainstream in the domestic high-end label industry, the traditional configuration of the process is the use of UV ink. Because the price of flexo UV ink is very expensive, it squeezes the cost space of the label, and because the UV ink itself has technical and environmental hazards, it starts with the reform process, and replaces the traditional UV with ink printing + UV coating. Flexo printing reduces costs and improves environmental protection. Is this scheme feasible? Here, the author analyzes this issue with everyone.
Response to the question of ink and wash
At present, the label industry still has doubts about the quality of ink, mainly including the following problems: 1 ink is not easy to adhere on the film material; 2 the ink dot is enlarged on the coated paper and film material, and it is difficult to control; 3 ink Drying too fast, the ink is easy to stick to the printing plate, causing blockage failure; 4Ink printing process needs to constantly monitor the fluctuation of pH value, and timely add pH stabilizer, the operation is inconvenient; 5 pH stabilizer contains ammonia water, It can lead to odors in the production environment and label products.
1. Adhesion on the film
In response to this problem, in fact, the division of labor between ink companies and printing companies should be very clear. Ink companies should know the matching characteristics of their products with the film, and should strictly control the solubility between the water-based resin and the film, that is, the polarity is similar, the solubility parameters are similar, and new hydrogen bonds should be generated. Printing companies should be able to use laboratory methods to analyze, select and screen out appropriate ink, pay attention not to easily veto, dump all the inks that are still defective, but do not blindly test the machine, increase the test cost.
2. Drying on the film
The main way of drying the ink on the film is volatilization, and drying is the main means. Therefore, the long-term solution to the drying problem is to increase the temperature, increase the air volume, slow down the speed or reduce the depth of the plate pocket. There is also a saying that ink drying is divided into three stages: the dry section is based on volatilization, allowing water to run away; then the relatively close of the binder molecules, extruding water; and finally the resin is solidified by intermolecular forces (including catalyst Cross-linking reaction under action).
One of the different arguments is the same, that is, the dry segments are volatilized, there is no other way. All other methods can only be followed by a drying tunnel to produce a chemical reaction under the influence of temperature, including desiccant technology. Therefore, it is still effective to determine the dryness of the ink surface by using the scraper fineness meter to determine the dry length of the ink. This method can know the speed of the ink drying speed before the machine is on, and can judge the failure probability of the printing on the machine. How high.
3. The dot expansion in printing
What is the difference in the print on the above picture? In fact, the viscosity of the ink, the viscosity of the ink and the UV ink are not on one level, and the difference between the two is 1 to 2 times. In other words, the expansion of the ink dot is related to its low viscosity. Then, can high-viscosity inks be used to solve the problem of network expansion? The answer is yes. The picture below shows a 150 line/inch 1% dot and a 175 line/inch 1% dot printed with high viscosity ink. From the arrangement spacing of adjacent dots, the diameter of the dot can be clearly distinguished. The viscosity of the ink is 15dPa s, which is twice the viscosity of the UV ink (7dPa s).
Why can I print with such high viscosity ink? Since a flexographic unit with an ink roller structure is used (as shown in the figure below), if a flexographic unit with a closed doctor blade structure is used, high-viscosity ink cannot be used. The root cause of determining the viscosity of the ink is the structure of the inking unit of the flexo press. On the same printing unit, the UV ink can be used for high viscosity. Why do you have to use low ink when using ink?
Flexographic unit with ink roller structure
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